Mercury capillary assembly



MERCURY CAPILLARY ASSEMBLY Filed Oct. 15, 1956 INVENTOR m4;- Kfl/FLMD/SC/f,

ATTORNEY fired States Patent 2,849,391 MERCURY CAPILLARY ASSEMBLY RolfKarl Ladisch, Lansdowne, Pa. Application October 15, 1956, Serial No.616,060

4 Claims. 01. 204-195 The general object of the present invention is toprovide an improved mercury capillary assembly.

In a prior art patent, No. 2,728,721, issued to myself and S. KnesbachDecember 27, 1955, there is described and claimed a novel polarographicelectrode assembly of the dropping mercury type for maintaining the rateof flow and the drop size of the mercury discharged by the assembly verynearly constant. In this invention, the assembly is maintained inservice by mercury being supplied from an inner reservoir to an outerreservoir through the action of a capillary side arm connected to theupper part of the inner reservoir, as is fully described in said patent.Due to the small cross-sectional area of the inner reservoir in relationto the cross-sectional area of the outer reservoir, only a relativelysmall portion of the overall charge of mercury can be stored andutilized for keeping the assembly in service during polarographicanalyses. The construction also sets up a pronounced meniscus of themercury at the tip of the capillary side arm between the inside wall ofthe outer reservoir and the outside wall of the inner reservoir, thusrendering the assembly sensitive to mechanical vibrations. Furthermore,the capillary side arm is bent at the place where it is connected to theinner reservoir and may trap and hold some of the mercury in the bend,thereby cancelling the desired valve action of the capillary side armuntil the mercury is removed from the bend of the side arm.

One of the objects of the present invention is to construct a droppingmercury assembly in such a manner that the greater portion of theoverall charge of mercury can be utilized for supplying the mercury tooperate the assembly. A further object is to minimize the dimensions ofthe assembly and yet to maintain the assembly operating in polarographictesting over a period of about two weeks with a single filling. Afurther object is to simplify the construction. A further object is toconstruct a capillary mercury assembly incorporating a capillary valvewhich contacts the upper surface of the mercury driving head at a placewhere the surface of the mercury is substantially plane and free of ameniscus. A further object is to employ a capillary valve having overits entire length a substantially straight bore. Other objects will beapparent from the following description of the preferred embodiment ofthe invention shown in the accompanying drawing forming a part of thisspecification. Said drawing is a longitudinal section through theassembly.

Referring particularly to the drawing, a tube 1, preferably ofpolymethylmethacrylate resin, is connected at its lower end to acapillary 2 by means of Tygon tubing 3. At its upper end, tube 1 mergeswith a lower reservoir 4, preferably of polymethylmethacrylate andpreferably having cylindrical form. Reservoir 4 is open to the airthrough vent 5. Placed on reservoir 4 is an upper reservoir 6,preferably of methylmethacrylate and preferably also having cylindricalform. Reservoir 6 has a glued-in-bottom 7, preferably ofpolymethylmethacrylate,

2,849,391 Patented Aug. 26, 1958 a threaded plug member 8 screwed intoits top, and a rubber or other collapsible bulb 9 fitted on member 8.Plug member 8 has a central port or air passage 14. Rubber ring 10between member 8 and reservoir 6 seals the reservoir 6 olf from theatmosphere. A tube 11 is tightly fitted into the bottom 7 of reservoir 6and extends downwardly to near the bottom of reservoir 4. A capillary12, preferably of polymethylmethacrylate and glued into the bottom 7 ofreservoir 6, extends upwardly to near the ceiling of reservoir 6 as wellas downwardly into reservoir 4, with its lower end being spaced abovethe lower opening of tube 11. The lower end of capillary 12 is drawn toa point or tip 13. Diameters of oneeighth of an inch for the bore intube 11 and 500 microns for the bore in capillary 12, have been foundsatisfactory for operating the assembly.

To operate the described assembly, member 8 including the collapsiblebulb 9 is unscrewed from the assembly. Instrument mercury M of highpurity is poured into reservoir 6, from where it flows through tube 11into reservoir 4. A suflicient amount of mercury M is introduced to fillreservoir 4 to near the height of vent 5. Member 8 including collapsiblebulb 9, together with rubber ring 10, are screwed back onto reservoir 6to seal the interior of reservoir 6 011 from the atmosphere. Thencollapsible bulb 9 is squeezed. This forces part of the air fromreservoir 6 out through tube 11 and capillary 12, this air escaping inbubbles through the mercury in reservoir 4 and leaving the assemblythrough vent 5. Then collapsible bulb 9 is relieved. Thereby, a partialvacuum is created in reservoir 6, and mercury flows from reservoir 4 upthrough tube 11 into reservoir 6. concomitantly, the level of themercury in reservoir 4 falls below the tip 13 of capillary 12. When thisoccurs, air from above the pool of mercury M in reservoir 4 flowsthrough capillary 12 into the upper part of reservoir 6. This lowers thevacuum in reservoir 6, and mercury flows down through tube 11 intoreservoir 4, until the level of the mercury pool rises to touch tip 13and hence seal capillary 12. The system is then balanced or stable. Butany withdrawal of mercury from capillary 2 causes the pool of mercury tosink below tip 13, which acts as a valve, with the same action asdescribed above. After a long period of operation, the supply of mercuryin reservoir 6 will be exhausted.

. Then the mercury may be replenished as described.

This assembly may be used in polarographic analyses employing droppingmercury electrodes or streaming mercury electrodes. In general, it willbe useful for maintaining a very nearly constant mercury overhead inapplications where a flow of mercury from a capillary under a drivinghead of mercury is involved.

What I claim is:

l. A dropping mercury capillary assembly comprising, in combination, abody having two separate mercury reservoirs, one directly above theother, both reservoirs being of substantially the same lateraldimensions; the upper reservoir having a top wall, and a bottom wallseparating it from the l wer reservoir; a collapsible elastomeric bulbsecured to said top Wall and being open to the upper reservoir so that,when it is collapsed and then released, it will create a partial vacuumin the upper part of the upper reservoir; the lower reservoir having inits upper portion a vent to the atmosphere and also having a bottomwall; a capillary that is straight throughout its length extending fromthe upper part of the upper reservoir through the bottom wall of theupper reservoir down to a level somewhat above the bottom wall of thelower reservoir, the lower end of said capillary being drawn down to apoint or tip; a mercury-conducting tube extending from the bottom of theupper reservoir nearly to the bottom wall of the lower reservoir, thelower end of said tube being below the lower pointed end of saidcapillary; a tube coupled to the bottom wall of the lower reservoir toconduct mercury therefrom; and a second capillary coupled to the lowerend of the lastnamcd tube toform drops of mercury;

2. The invention defined in claim 1, wherein there is a removable plugmember-sealed into the top-wall-of theupper reservoir; said plug" memberhaving anair passage extendingtherethrough fronrtop to bottom, said bulbbeing fitted 'onsaid plug member-fsaid'plug member, when removed, givingaccessto; the; interior of the body forthe introduction of' mercur'ytherein.

3. The iHVCDlZlQHdCfiIlGd'ill-Claim 2 wherein theremovable plug memberis 'screwed into the top wall of the upper reservoir; at; the cententhereof; the mercuryconducting tube' is located near" the innerperipheries of-the upper and-lowerreservoirs;;the capillary that extendsthrough the bottomw-allof the; upper reservoir is in thecenter ofsaid-bottom-wallj-and' the tube that is coupled to the bottom wall ofthelower reservoir is directly belowthe pointed lower end ofthelast-named capillary.

4; A dropping mercuryt capillary assembly comprising, in combination, abody having two separate mercury reservoirs, one directly above theother and both reservoirsbeing of substantiallythe samelateraldimensions; the-upper reservoir having atop wall'and a bottom wallseparating it from thelower reservoir; a collapsible elastomericbulbsecuredto'saidtopwall and-open to the upper reservoir so that, when itis collapsed and then released, itwillcreatea-partial vacuum in theupper part of the upper reservoir thereby to draw mercury up into theupper reservoir; the lower reservoir having in its upper portion a ventto the atmosphere and also having a bottom wall; a mercury-conductingtube extending from the bottom of the upper reservoir nearly to thebottom wall of the lower reservoir; a capillary that is straightthroughoutits length extending from the upper part of the upperreservoir through the bottom wall of the upper reservoir down to a levelsomewhat above the bottom wall of the lower reservoir, but higher thanthe lower end of said mercury-conducting tube; the lower end of saidcapillary beingdrawn'down to a point or tip; a tube coupled to thebottom wall of the lower reservoir to conduct mercury therefrom; asecond capillary coupled to the lower end of the last-named tube to formdrops of mercury at its lower end; there being a supply of mercury insaid reservoirs sufiicient to-form a shallow pool of mercury on thebottom wall'of the lower reservoir with the'mercury presenting asubstantially plane upper surface of relatively very large area comparedto said point or tip which contacts it.

2,728,721 Ladisch et a1. Dec. 27, 1955

1. A DROPPING MERCURY CAPILLARY ASSEMBLY COMPRISING, IN COMBINATION, ABODY HAVING TWO SEPARATE MERCURY RESERVOIRS, ONE DIRECTLY ABOVE THEOTHER, BOTH RESERVOIRS BEING OF SUBSTANTIALLY THE SAME LATERIALDIMENSIONS; THE UPPER RESERVOIR HAVING A TOP WALL, AND A BOTTOM WALLSEPARATING IT FROM THE LOWE RESERVOIR; A COLLASIBLE ELASTOMERIC BULBSECURED TO SAID TOP WALL AND BEING OPEN TO THE UPPER RESERVOIR SO THAT,WHEN IT IS COLLAPSED AND THEN RELEASED, IT WILL CREATE A PARTIAL VACUUMIN THE UPPER PART OF THE UPPER RESERVOIR; THE LOWER RESERVOIR HAVING INITS UPPER PORTION A VENT TO THE ATMOSPHERE AND ALSO HAVING A BOTTOMWALL; A CAPILLARY THAT IS STRAIGHT THROUGHOUT ITS LENGTH EXTENDING FROMTHE UPPER PART OF THE UPPER RESERVOIR THROUGH THE BOTTOM WALL OF THEUPPER RESERVOIR DOWN TO A LEVEL SOMEWHAT ABOVE THE BOTTOM WALL OF THELOWER RESERVOIR, THE LOWER END OF SAID CAPILLARY BEING DRAWN DOWN TO APOINT OR TIP; A MERCURY-CONDUCTING TUBE EXTENDING FROM THE BOTTOM OF THEUPPER RESERVOIR NEARLY TO THE BOTTOM WALL OF THE LOWER RESERVOIR, THELOWER END OF SAID TUBE BEING BELOW THE LOWER POINTED END OF SAIDCAPILLARY; A TUBE COUPLED TO THE BOTTOM WALL OF THE LOWER RESERVOIR TOCONDUCT MERCURY THEREFROM; AND A SECOND CAPILLARY COUPLED TO THE LOWEREND OF THE LASTNAMED TUBE TO FORM DROPS OF MERCURY.